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An Overview of GPRS

An Overview of GPRS. Shourya Roy Pradeep Bhatt Gururaja K. What is GPRS?. A new bearer service for GSM that greatly improves and simplifies wireless access to packet data networks,e.g to the internet. Motivation . Speed Immediacy New and better applications User friendly billing.

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An Overview of GPRS

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  1. An Overview of GPRS Shourya Roy Pradeep Bhatt Gururaja K.

  2. What is GPRS? • A new bearer service for GSM that greatly improves and simplifies wireless access to packet data networks,e.g to the internet.

  3. Motivation • Speed • Immediacy • New and better applications • User friendly billing

  4. GSM Architecture PSTN PDN ISDN GMSC BSC BTS MS MSC BTS BSC EIR MS AUC HLR BTS VLR MS

  5. GPRS Architecture Other GPRS PLMN GGSN Gp Gn SGSN Gb Gf BSC Gr Gs Gi BTS Gc GGSN PDN EIR D BTS HLR MS MSC/VLR

  6. Protocol Architechture • Transmission Plane GPRS specifies a tunnel mechanism to transfer user data packets . • Signalling Plane GTP specifies a tunnel control management protocol.The signalling is used to create modify and delete tunnels.

  7. Registration of a Mobile Node A mobile station must register itself with GPRS network. • GPRS attach • GPRS detach GPRS detach can be initiated by the MS or the network.

  8. Session Management After Successful attach a MS gets one or more Packet Data Protocol(PDP) address.This address is unique only for a particular session. It consists of, • PDP type • PDP address assigned to MS • Requested QoS • Address of the corresponding GGSN

  9. Session Management(Contd.) PDP-Address allocation: • Static:Assigned by network operator of User’s home PLMN. • Dynamic:Assigned by Corresponding GGSN.

  10. PDP Context Activation MS SGSN GGSN Activate PDP Context Request PDP type,PDP Address QoS Requested,Access Point,… Security Functions Create PDP Context Request PDP type,PDP Address QoS Negotiated,Access Point,… Create PDP Context Response Activate PDP Context Accept PDP type,QoS Negotiated,… PDP type,PDP Address QoS Negotiated,…

  11. Routing BSC BTS BSC BTS SGSN SGSN MS Inter-PLMN GPRS Backbone Gn Intra-PLMN GPRS Backbone Intra-PLMN GPRS Backbone Gp PLMN2 PLMN1 Border Gateway Gn Border Gateway Gn GGSN Packet Data Network(PDN) Eg.Internet,Intranet SGSN Gi GGSN Host Router LAN

  12. Location Management • MS frequently sends location update messages to inform the SGSN where it is. • Determining frequency of update messages is non-trivial. • The location update frequency is dependent on the state of the MS.

  13. Location Management(Contd.) A MS can be in 3 states: • IDLE • READY • STANDBY

  14. Protocol Architechture Transmission Plane The protocols provide transmission of user data and its associated signalling Signalling Plane Comprises protocols for the control and support of functions of the transmission plane

  15. Transmission Plane GPRS Backbone:SGSN GGSN GTP tunnels the user packets and related signalling information between the GPRS support nodes. Subnetwork dependent convergence protocol It is used to transfer packets between SGSN and MS Data link layer LLC(MS-SGSN) RLC/MAC(MS-BSS) Physical layer PLL:channel coding,detection of errors, forward error correction, interleaving, detection of physical link congestion RFL:modulation and demodulation

  16. Network Layer (IP or X.25) Relay SNDCP GTP GTP LLC TCP/UDP TCP/UDP Relay RLC BSSP BSSGP IP IP MAC Network Service Network Data Link Service Service Data Link Layer PLL RFL Phy Layer Phy Layer Phy Layer Phy layer Gm Gb Gi BSS SGSN GGSN RLC :Radio link control BSSGP:BSS GPRS Application protocol PLL :Physical link layer GTP :GPRS tunneling protocol RFL :Physical RF layer TCP :Transmission control protocol MAC:Medium access control UDP :user datagram protocol IP :Internet Protocol Transmission Plane

  17. MS BSS Application Network Layer SNDCP LLC RLC Relay RLC BSSGP MAC MAC Network Service PLL RFL PLL PHY RFL Layer Um SNDCP:Subnetwork dependent convergence protocol LLC :Logical link control RLC :Radio link control

  18. SGSN BSS MS GMM/SM GMM/SM LLC LLC Application Relay RLC BSSGP BSSGP RLC Application MAC Network layer MAC Network service GSM/RF GSM RF Physical layer Phy Layer Um Gb GMM/SM:GPRS Mobilty Management and session Management Protocol GSM/RF:GSM physical layer(radio interface) I.e.PLL and RFL Signalling Plane:MSSGSN

  19. SGSN MSC/VLR BSSAP BSSAP SCCP SCCP MTP3 MTP3 MTP2 MTP2 Phy Layer Phy Layer Gs Signalling Plane SGSN MSC/VLR

  20. SGSN HLR(and EIR) MAP MAP TCAP TCAP SCCP SCCP MTP3 MTP3 MTP2 MTP2 Phy Layer Phy Layer Gr MAP :Mobile Application Part TCAP :Transaction capabilities and application part SCCP :Signalling connection control part MTP :Message transfer part Signalling Plane SGSNHLR/SGSNEIR

  21. GSM TDMA Frame Slots and Bursts 960 MHz 959.8 MHz 124 Time Slot 123 . . . 200 KHz . . . Downlink 1 2 3 4 5 6 7 8 1 2 TDMA Frame 935.2 MHz 1 935 MHz 915 MHz Data Burst = 156.25 bit periods 914.8 MHz 124 123 . . . 200 KHz . . . 1 2 3 4 5 6 7 8 1 Uplink 2 TDMA Frame 890.2 MHz 1 890 MHz

  22. GPRS Air Inteface Time Slot Number 0 0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 0 0 1 1 2 2 3 3 4 4 F1 Uplink F2 F3 F4 Carrier Frequency 0 0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 0 0 1 1 2 2 3 3 4 4 F1 F2 Downlink F3 F4 Voice User1 GPRS User1 GPRS User3 Voice User2 GPRS User2

  23. GPRS Air Interface • Master slave concept • One PDCH acts as Master • Master holds all PCCCH channels • The rest of channels act as Slaves • Capacity on demand • PDCH(s) are increased or decreased according to demand • Load supervision is done in MAC Layer

  24. GPRS Logical Channels Function Group Channel Direction Packet data Traffic channel PDTCH Data Traffic MS BSS Packet broadcast control channel PBCCH Broadcast Control MS BSS PRACH Random Access MS BSS Packet common Control Channel (PCCCH) PAGCH Access Grant MS BSS PPCH Paging MS BSS PNCH Notification MS BSS PACCH Associated Control MS BSS Packet Dedicated Control Channels PTCCH Timing Advance Control MS BSS

  25. Uplink Data Transfer MS BSS Packet channel Request PRACH or RACH Packet Immediate assignment PAGCH or AGCH Packet resource Request PACCH Packet resource assignment PACCH Random Access Transmission Frame Transmission PDTCH Negative Acknowledgement PACCH Retransmission of blocks in error PDTCH Acknowledgement PACCH

  26. Downlink Data Transfer MS BSS Packet paging request PPCH or PCH Packet channel Request PRACH or RACH Packet Immediate assignment PAGCH or AGCH Packet paging response PACCH Packet resource assignment PACCH or PAGCH Paging Frame Transmission Transmission PDTCH Negative Acknowledgement PACCH Retransmission of blocks in error PDTCH Acknowledgement PACCH

  27. Multi Slot Operation • GPRS allows a mobile to transmit data in up to 8 PDCHs (eight-slot operation) • 3-bit USF at beginning of each radio block in downlink points to next uplink radio block • Comparison with single-slot GSM • Higher delay at higher load • Low blocking rate • Improved Throughput

  28. Conclusion • GPRS provides efficient access to Packet Data Networks. • Multislot operation in GPRS leads to efficient channel utilization. • GPRS is more effective for long data packet transmission than short ones.

  29. References • “General Packet Radio Service in GSM”, Jian Cai and David J. Goodman, Rutgers University, IEEE Communications Magazine, Oct 1997 • http://www.comsoc.org/pubs/surveys/3q99issue/bettstetter.html • http://www.wsdmag.com/2000/aug2200/38-45.html • “Wireless Internet Access based on GPRS”, IEEE Personal Comm. April 2000.

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